MRI

If the patient doesn’t have tremor or much asymmetry or has other red flags (supranuclear gaze palsy, no response to dopaminergic therapy, lower-half parkinsonism or history of strokes, Babinski sign present, urinary incontinence or unexplained sexual dysfunction, history of cancer or an immunocompromised state, early falls) then an MRI of the brain without contrast would certainly be appropriate and recommended.

Apomorphine Test

Other Tests

You may want to consider other tests when making the diagnosis:

Complete blood cell count and sedimentation rate (Note: if you are considering using clozapine or if your patient is taking clozapine, a white blood cell count would be appropriate due to the risk of agranulocytosis)

Chemistry

Urine analysis

BUN & creatinine

Thyroid analysis

Liver function

Serum ceruloplasmin

Copper levels

Polysomnography, if a patient has insomnia and/or excessive diurnal somnolence (also if a patient is fighting or talking in his sleep)

Notwithstanding all the previously mentioned tests, the diagnosis of PD remains clinical. Perhaps one of the best predictors of a diagnosis of PD is a relatively slow, gradual progression and a sustained response to levodopa or other dopaminergic therapies.